Cement kiln tail flue gas catalytic oxidation desulfurization method

Abstract

The invention discloses a cement kiln tail flue gas catalytic oxidation desulfurization method. A multistage preheater and a dust collector, and a kiln tail flue gas conveying pipeline which is used for connecting the multistage preheater and the dust collector are adopted to catalytic oxidation desulfurization. The method specifically comprises the following steps: (1) preparing an aqueous solution containing a metal ion catalyst from a metal compound; (2) atomizing and spraying the aqueous solution of the metal ion catalyst into the multistage preheater or / and the kiln tail flue gas conveying pipeline, instantaneously drying in high-temperature flue gas to form a nanoscale molecular state desulfurization catalyst, and quickly and fully mixing the nanoscale molecular state desulfurizationcatalyst with the flue gas; (3) in a high-temperature environment, subjecting SO2 molecules, O2 molecules, CaCO3 powder and CaO powder to a desulfurization reaction rapidly and fully under the actionof the molecular state desulfurization catalyst; and (4) aggregating generated CaSO4 particles under the action of molecular H2O, collecting the aggregated CaSO4 particles through the dust collector,and enabling the collected CaSO4 particles to enter a cement clinker system again. The method for desulfurization has the characteristics of low cost, high reliability, high desulfurization efficiency and the like.

Description

technical field [0001] The invention relates to the field of air pollution prevention and control, in particular to a catalytic oxidation desulfurization method for cement kiln tail flue gas. Background technique [0002] Limestone is the main raw material of cement plants, accounting for about 80% of all raw materials, and the sulfur content of limestone used in most cement plants is very low, which will not cause SO 2 However, high-quality limestone is a non-renewable mineral resource. It is not only used in cement production, but also in thermal power, metallurgy, papermaking, steel, pharmaceuticals, food additives, sugar, chemicals, pesticides and other industries. The mining of high-quality limestone is exhausted, and some cement plants have to use low-grade high-sulfur limestone with a sulfur content ranging from 0.2% to 3.0%, resulting in SO in cement kiln flue gas 2 The emission concentration is as high as 1000-4000mg / Nm 3 . However, China's "Emission Standard of ...

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Problems solved by technology

Supported catalytic desulfurization, for example, the patent application with application number 201810982409.6 discloses a preparation method of highly dispersed desulfurization catalyst: (1) using soluble salt as raw material, preparing a solution with salt and water; (2) adding lye for co-precipitation , enter the aging stage after the precipitation is completed; (3) Turn on the stirring, and transport the aged mixture to the plate and frame filter through the pump to filter, wash with water to remove impurity ions to obtain solid precipitation; (4) Spray drying to obtain massive solids; ( 5) Extrude the binder and block solid into strips; (6) The formed product is dried and then roasted to obtain a highly dispersed desulfurization catalyst. This technology mainly uses a similar SCR denitrification mode for loaded desulfurization, but there are the following problems : First, the process is complicated and the cost is high; second, there are problems such as blockage and failure of the catalytic module; third, the contact time is short. Generally, the wind speed of the flue gas at the kiln tail is 10-18m / s, and the contact time at the catalytic module is 0.3s The following results in the inability to fully catalyze the reaction. Fourth, the inability to ensure stable and low-emission desulfurization

Catalytic desulfurization supported by liquid phase. For example, in the "Study on Flue Gas Desulfurization of Iron Ion Liquid Phase Catalytic Oxidation" published by the team of Professor Zhang Yu of Dalian University of Technology, a liquid-loaded catalyst is used for desulfurization in the laboratory. Catalyst aqueous solution adsorbs SO 2 , can achieve nearly 100% desulfurization under certain conditions; but there is also the problem of liquid-gas phase interface reaction, the reaction efficiency is not high, when the temperature exceeds 60 ° C, the adsorption of SO 2 The ability is poor. If a large amount of water is used to reduce the flue gas temperature, there will be waste of water resources and white plumes, so it cannot be promoted in actual production.

Unloaded catalytic desulfurization, such as the application number 201711190438.0 patent application discloses a catalytic desulfurizer for reducing sulfur dioxide emissions in cement enterprises, including two parts of powder and water, the mass percentage of each component of the powder is, calcium carbonate: 45~ 65%, calcium oxide: 28-45%, iron oxide: 0.1-1%, magnesium oxide: 1-6.5%, barium carbonate: 0.5-1.5%, rare element compound: 1-5%, silicon dioxide: 3- 5.5%, achievable SO 2 90% emission reduction, SO 2 Displacement≤100mg / m 3 , this type of catalytic desulfurization uses transition metal or alkali metal oxides to make powder or suspension to catalyze the oxidation of SO 2 To achieve desulfurization, but there are the following problems: first, the use of rare metals as the liquid phase as the catalyst, the cost is high; second, the suspension is easy to block, and the reliability is poor; third, the particle size of the suspension is large, and it is generally difficult to achieve With a fineness of 500 mesh (26 microns), the catalytic effect is unstable, and it cannot meet the high-sulfur ore used in cement kilns and the kiln tail flue gas SO 2 Requirements for emission exceeding the standard and not exceeding the standard

[0005] To sum up, the SO2 caused by the use of high-sulfur ore in cement plants is currently 2 Excessive emissions, there is no mature desulfurization technology with low cost and reliable operation